Over the first four years of life children make tremendous strides in acquiring the social skills that are essential for the lifelong development of healthy relationships. They learn how to engage with other children and adults, and develop skills in negotiation, the co-regulation of play, and sustaining friendships. The current investigation, to which the proposed supplemental project is linked, is following two temperament groups - infants who are temperamentally fearful and those who are temperamentally exuberant - for whom prior evidence suggests these early social tasks are particularly challenging. The study is focusing on the contribution of maternal caregiving behaviors and the development of information processing skills as they influence the trajectories of these children towards regulated or unregulated social behavior between infancy and age four years. During this same period, most children in the U.S. enter child care environments with other children which, as a result, provide a critical arena for social development. Early social development has figured prominently in the child care literature and is now a focal point of research in light of evidence that, of the range of developmental outcomes examined, social behavior may be particularly susceptible to variation in the amount and quality of child care the children experience. The supplemental project would add to the current investigation an examination of the critically important mediating influence of child care environments. By examining the children's exposure to child care with peers from early infancy through preschool, as well as their experiences in child care when they are 24, 36 and 48 months of age, this project would significantly expand our understanding of the kinds of experiences that either increase or decrease the odds of compromised social development among temperamentally vulnerable infants during a crucial period when their trajectories begin to diverge towards adaptive or maladaptive outcomes. On-site child care assessments will focus on the quality of caregiving the children receive, the extent to which their caregivers support positive peer interactions in child care, and the children's actual peer experiences in child care. These data will supplement the growth models being employed in the current study to include child care among the processes that affect the development of adaptive or maladaptive social behavior among temperamentally vulnerable infants. [unreadable] [unreadable]